20 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
in reality widely different, being, in fact, a near relative of 
the Razor-bills and Guillemots of our own seas. These 
latter birds, like other members of the Alcide, make active 
use of their wings in diving, as anyone may have noticed 
who has watched these birds diving in an aquarium; but 
their use in this direction has not prevented them retaining 
the power of flight, though they are, comparatively speak- 
ing, rather feeble fliers. In the Great Auk, however, the 
specialization of the wing as a diving organ had advanced 
so far that it had wholly lost its capacity for aerial pro- 
eression, but there seems no doubt that it formed an 
efficient paddle, though one framed on a different pattern 
to that of the Penguin. The anterior limbs were there- 
fore truly functional, although functional in the medium 
water only, and in harmony with this fact the well- 
developed keel to the sternum is noteworthy. The extinc- 
tion of this interesting bird, which appears to have been 
completed shortly before the middle of the present century, — 
was wholly accomplished by the destructive propensities 
of the genus Homo, the helplessness of this bird at its 
breeding stations causing it to fall an easy prey to the 
destroyer. ; 
I now come to the third and last division of my subject, 
that, namely, which deals with those flightless birds which 
have lost the use of their wings without having obtained 
any compensating advantages in other directions. The 
birds in this group belong to very different families, all 
however, included in the Carinate sub-class, and they are all 
strictly degenerates. When speaking of the members of 
the first group—Hesperornis and the Ratites—I remarked 
that these birds, many of them, had survived to the 
present day by virtue of their capacity to cope with the 
enemies with which they came into contact. The mem- 
bers of the present group, however, may be said to 
